: Rhaponticum repens, Centaurea picris
: Introduced to North America in the early 1900's. Toxic to horses. This species is listed as a prohibited noxious weed by the Michigan Department of Agriculture.
: Perennial herb that can grow up to 3 ft (1m) tall. Tap root can reach up to 8 ft and has horizontal and vertical roots. Roots can be brown to black in color and scaly.
: Basal leaves are lobed and 2-4 in long while upper leaves are smaller have smooth margins. Covered with dense gray hairs.
: Originate from a basal rosette of leaves; erect, covered in dense gray hairs, 1-3 ft (18-36 in) tall, with many branches.
: Pink, purple or white in color, turn straw color as they mature. Flower heads are solitary, urn-shaped and approximately 0.25 - 0.5 in in diameter; blooms from summer to fall.
Fruit and seeds
: Produces 50-500 seeds per shoot which are viable for 2-3 years in soil. Fruits are ivory colored with a tuft of hair that falls off at maturity.
: Native to Eurasia specifically southern Ukraine, southeast Russia, Iran and Mongolia. Found in disturbed sites, along roadsides, riverbanks, irrigation ditches, pastures, waste places, clear-cuts, and croplands.
: Primary reproduction is vegetatively and second is by seed.
: Brownray knapweed (Centaurea jacea
), Meadow knapweed (Centaurea xmoncktonii
); Spotted knapweed (Centaurea stoebe
); Common crupina (Crupina vulgaris
Monitoring and rapid response
: One of the most difficult to control. Hand pull and treat with herbicides for small infestations. Biologically controlled by the Russian knapweed gall nematode and the Russian knapweed mite.
: The information provided in this factsheet was gathered from the Bugwood.org wiki and Colorado State University Extension.
Individual species images that appear with a number in a black box are courtesy of the Bugwood.org network (http://www.invasive.org).Individual photo author credits may not be included due to the small display size of the images and subsequent difficulty of reading the provided text. All other images appear courtesy of Google (http://images.google.com).